In a typical computer network, the network peers send and receive data packets. Each packet of data follows a particular path from source peer to the destination peer. Generally, the network peers or nodes are connected using tree type topology or Ring topology.
In tree topology, path of a data packet is in the form of a tree wherein of network nodes are connected to each other. The data packets are sent from source to destination in a single unique path using a particular tree formation protocol.
Different tree formation protocols are known in the art including spanning tree protocol (STP), Rapid STP (RSTP), Multiple STP (MSTP) etc. The STP protocol is a Data Link Layer protocol defined in IEEE 802.1D. It creates a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches), and disables those links that are not part of the spanning tree, thereby leaving a single active path between any two network nodes.
Since STP is a slow mechanism, advanced and faster mechanisms were invented including the RSTP that provides for faster spanning tree convergence after a topology change and the MSTP that is an extension to RSTP to further develop the usefulness of virtual LANs (VLANs). This is a “Per-VLAN” Multiple Spanning Tree Protocol and hence configures a separate Spanning Tree for each VLAN group and blocks all but one of the possible alternate paths within each Spanning Tree.
In the ring network topology, each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node—a ring. Data travels from node to node, with each node along the way handling every packet.
Whatever fashion the nodes may be connected in a network, any fault in the nodes and failure of path will disturb the data traffic. Thus restoration of faulty nodes and links are essential to ensure successful flow of the data traffic.
Various methods for restoring the faults are known in the art. These methods are based on the type of topology in which the nodes are connected to each other. For example in case of STP and RSTP, whenever there is a fault in the link, the nodes associated to that particular link will send a topology change message in the packet. Whichever node reads this message changes its topology and begins to form a new tree.
For a ring topology such as Ethernet Ring Protection Switching, (ERPS), protection and recovery switching is made by flushing or deleting all information learned by a node whenever that particular node receives the topology change message. Thereby, ensuring that there are no loops are formed at the Ethernet layer.
FIG. 1 illustrates how different restoration mechanism A, B, and C is applied on different network topologies A, B and C respectively as known in the prior art to restore the fault links. It is therefore apparent from FIG. 1 that recovery of a fault in the data path between a pair of nodes depends upon the type of topology in which the nodes are connected to each other in a network.
For high level working environments like VLAN, MAC, IP, QoS etc, a novel method for fault restoration is needed.